Background: The incidence of early-onset colorectal cancer (eoCRC) has been reported to increase, and patients with eoCRC seem to be diagnosed at more advanced stages compared to elderly patients. The aim of this study was to describe patient and disease characteristics, symptomatology and the incidence of eoCRC in a national cohort. Materials and methods: 521 eoCRC patients (≤40 years old) diagnosed with histologically verified colorectal cancer (CRC) during the years 2001–2013 were identified in national databases and compared to more than 15,000 CRC patients aged 66–75 years. Age-adjusted incidence was calculated for eoCRC patients and various sub-analyses were performed. Results: More advanced stages were seen in eoCRC patients compared to elderly patients (stage II: p < 0.001, III: p = 0.01 and IV: p < 0.01). Differences were statistically significant in colon cancer, but not in rectal cancer. A significant difference in sex distribution was seen between right and left-sided tumors in the eoCRC group. The age-adjusted incidence rate increased during the study period (1.60–2.55 per 100.000), and significant annual percent changes (APC) were seen in young females (APC = 4.73) and left-sided tumor localization (including rectal cancer) (APC = 4.54), respectively. Conclusion: In this nationwide cohort of eoCRC patients, our results confirm that young patients are diagnosed at advanced stages, and that the incidence of eoCRC is increasing.